International Patent Application No. PCT/AU2005/000580 published under WO 2005/103926 (to which U.S. patent application Ser. No. 11/111,946 and published under No. 2005-0262313 corresponds) in the name of the present applicant, discloses how different portions of an application program written to execute on only a single computer can be operated substantially simultaneously on a corresponding different one of a plurality of computers. That simultaneous operation has not been commercially used as of the priority date of the present application. International Patent Applications Nos. PCT/AU2005/001641 (WO2006/110,937) and PCT/AU2006/000532 (WO2006/110,957) both in the name of the present applicant and both unpublished as at the priority date of the present application, also disclose further details. The contents of the specification of each of the above-mentioned prior application(s) are hereby incorporated into the present specification by cross reference for all purposes.
Briefly stated, the abovementioned patent specification discloses that at least one application program written to be operated on only a single computer can be simultaneously operated on a number of computers each with independent local memory. The memory locations required for the operation of that program are replicated in the independent local memory of each computer. On each occasion on which the application program writes new data to any replicated memory location, that new data is transmitted and stored at each corresponding memory location of each computer. Thus apart from the possibility of transmission delays, each computer has a local memory the contents of which are substantially identical to the local memory of each other computer and are updated to remain so. Since all application programs, in general, read data much more frequently than they cause new data to be written, the abovementioned arrangement enables very substantial advantages in computing speed to be achieved. In particular, the stratagem enables two or more commodity computers interconnected by a commodity communications network to be operated simultaneously running under the application program written to be executed on only a single computer.
In many situations, the above-mentioned arrangements work satisfactorily. This applies particularly where the programmer is aware that there may be updating delays and so can adjust the flow of the program to account for this. However, the need to update each local memory when any change is made to any memory location, can create contention where corresponding memory locations are being updated in simultaneous or near simultaneous fashion from different sources. This can establish a race condition or similar anomalous conditions. Such conditions can also arise in other computing, information processing, electronics, and electrical engineering situations. It is towards the detection and resolution of contention or a race condition that the present invention is directed.